It is well known to link electronic documents by setting up hyperlinks between documents in HTML format stored at, and transferable between, computers forming nodes of a conventional computer network, e.g. the Internet or an intranet. See Berners-Lee, T. J., Cailliau, R., and Groff, J.-F., The Worldwide Web, Computer Networks and ISDN Systems 25, North-Holland, 1992, pp. 454-459.
Soderg.ang.rd, C., Juhola, H., Backstrom, C., and Vainikainen, I., "A Pen Scanner Based System For An Easy Access to Relevant WWW Hyperlinks", in Proceedings of TAGA '97 Conference, Quebec, Calif., May 4-7, 1997, Technical Association for Graphic Arts, 1997, describe a system in which a pen scanner enters printed anchor words linked to uniform resource locator (URL) addresses. The scanned text is processed with optical character recognition (OCR), and the OCR result is processed in an interpretation module to select a correct link anchor from a locally stored link list that has been downloaded from the publisher's World Wide Web (WWW) server. After selecting the link anchor, the corresponding URL addresses are determined from the link list and the WWW pages are retrieved with an Internet browser and displayed on a monitor.
Robinson, P., Sheppard, D., Watts, R., Harding, R., and Lay, S., "A framework for interacting with paper", EUROAGRPHICS '97, Vol. 16, No. 3, 1997, pp. C-329 to C-334, describe a framework for preparation and presentation of mixed-media documents using a registry that associates physical locations on pieces of paper with actions. A DigitalDesk, which has a video camera mounted above a desk to detect where a user is pointing and to read documents on the desk and a projector mounted above the desk to project objects onto the work surface and paper documents, is used to identify pieces of paper and animate them by placing them on the DigitalDesk. The camera identifies the document and follows the pointer, and associated actions are identified in the registry and invoked as appropriate with the results being projected back onto the paper. To identify a document, a page is marked with a unique OCR font identifier that encodes the location of the directory as a network IP address and an index for the document within the directory. A document can be printed from the registry, with its unique identifier; a printed document's page representation is retained in the registry as an immutable copy of its structure. Paper access to the World Wide Web is possible. Given a URL, information on the associated web page can be captured in the registry, the page can be printed, and links can be activated by placing the paper on a DigitalDesk and pointing. The page's identifier and the coordinates of the link are looked up in the registry to yield the appropriate activity, and the results are projected back onto the desk.
Johnson, W., Jellinek, H., Klotz, L., Rao, R., and Card, S., "Bridging the Paper and Electronic Worlds: The Paper User Interface", INTERCHI '93 Conference Proceedings, ACM, 1993, pp. 507-512, describe techniques in which documents can contain, in addition to the human-readable information (e.g. text), printed machine-readable encoded data. The document can, for example, be a form and the encoded data can be a form identifier. A prototype system can receive a faxed form and decode the form identifier, locate an appropriate action description file, process the page image, and provide the information from the page image to the action procedure for the form. The system automatically creates a new form that points at a newly stored document, to give the user a way of accessing and interacting with it later, with checkboxes that allow the user to print or delete it.
U.S. Pat. No. 5,661,506 describes a pen and paper information recording system using an imaging pen. A writing paper has a writing surface and a prerecorded invisible pattern of pixels. Each pixel contains encoded, optically readable position information that identifies a coordinate position on the writing surface, and may also include a page number and a pad number. The system includes an imaging system for providing image signals representing images of pixels near the pen tip. A processor responds to the image signals and determines and electronically records positions of the pen tip on the writing surface as markings are made.
U.S. Pat. No. 5,486,686 describes machine readable electronic domain definitions of part or all of electronic domain descriptions of hardcopy documents and/or of part or all of the transforms that are performed to produce and reproduce such hardcopy documents, encoded in codes that are printed on the documents. The codes permit the electronic domain descriptions of the documents and/or the transforms to be recovered more robustly and reliably when the information carried by the documents is transformed from the hardcopy domain to the electronic domain. Encoded data embedded in the hardcopy document may include descriptions of the data points for structured graphics, descriptions of algorithms utilized for performing computations for spreadsheets, descriptions of hypertext pointer values, descriptions of structural characteristics of an electronic source document, descriptions of a document editor, descriptions of file name and storage location of an electronic source document, and descriptions of audit-trail data for an electronic source document.